added CI content

.github/workflows/build_containers.yml

@@ -0,0 +1,26 @@
+name: build and publish containers
+on: workflow_dispatch
+permissions:
+  contents: read
+  packages: write
+jobs:
+  build:
+    name:
+    runs-on: ubuntu-latest
+  steps:
+    - name: check out the repo
+      uses: actions/checkout@v4
+    - name: setup Docker Buildx
+      uses: docker/setup-buildx-action@v3
+    - name: Login to github container repo
+      uses: docker/login-action@v3
+      with:
+        registry: ghcr.io
+        username: ${{ github.actor }}
+        password: ${{ secrets.GITHUB_TOKEN }}
+    - name: build+push
+      uses: docker/build-push-action@v5
+      with:
+        context: "{{defaultContext}}:dnsmasq-dhcpd-dynamic"
+        push: true
+        tags: dnsmasq:dyanmic-test